Cross-regulation of cytokine signalling: Pro-inflammatory cytokines restrict IL-6 signalling through receptor internalisation and degradation

in Journal of Cell Science (2010), 123(6), 947-959

The inflammatory response involves a complex interplay of different cytokines which act in an auto- or paracrine manner to induce the so-called acute phase response. Cytokines are known to crosstalk on ... [more ▼]

The inflammatory response involves a complex interplay of different cytokines which act in an auto- or paracrine manner to induce the so-called acute phase response. Cytokines are known to crosstalk on multiple levels, for instance by regulating the mRNA stability of targeted cytokines through activation of the p38-MAPK pathway. In our study we discovered a new mechanism that answers the long-standing question how pro-inflammatory cytokines and environmental stress restrict immediate signalling of interleukin (IL)-6-type cytokines. We show that p38, activated by IL-1b, TNFa or environmental stress, impairs IL-6-induced JAK/STAT signalling through phosphorylation of the common cytokine receptor subunit gp130 and its subsequent internalisation and degradation. We identify MK2 as the kinase that phosphorylates serine 782 in the cytoplasmic part of gp130. Consequently, inhibition of p38 or MK2, deletion of MK2 or mutation of crucial amino acids within the MK2 target site or the di-leucine internalisation motif blocks receptor depletion and restores IL-6-dependent STAT activation as well as gene induction. Hence, a novel negative crosstalk mechanism for cytokine signalling is described, where cytokine receptor turnover is regulated in trans by pro-inflammatory cytokines and stress stimuli to coordinate the inflammatory response. [less ▲]

Principles of interleukin (IL)-6-type cytokine signalling and its regulation

in Biochemical Journal (2003), 374(Pt 1), 1-20

The IL (interleukin)-6-type cytokines IL-6, IL-11, LIF (leukaemia inhibitory factor), OSM (oncostatin M), ciliary neurotrophic factor, cardiotrophin-1 and cardiotrophin-like cytokine are an important ... [more ▼]

The IL (interleukin)-6-type cytokines IL-6, IL-11, LIF (leukaemia inhibitory factor), OSM (oncostatin M), ciliary neurotrophic factor, cardiotrophin-1 and cardiotrophin-like cytokine are an important family of mediators involved in the regulation of the acute-phase response to injury and infection. Besides their functions in inflammation and the immune response, these cytokines play also a crucial role in haematopoiesis, liver and neuronal regeneration, embryonal development and fertility. Dysregulation of IL-6-type cytokine signalling contributes to the onset and maintenance of several diseases, such as rheumatoid arthritis, inflammatory bowel disease, osteoporosis, multiple sclerosis and various types of cancer (e.g. multiple myeloma and prostate cancer). IL-6-type cytokines exert their action via the signal transducers gp (glycoprotein) 130, LIF receptor and OSM receptor leading to the activation of the JAK/STAT (Janus kinase/signal transducer and activator of transcription) and MAPK (mitogen-activated protein kinase) cascades. This review focuses on recent progress in the understanding of the molecular mechanisms of IL-6-type cytokine signal transduction. Emphasis is put on the termination and modulation of the JAK/STAT signalling pathway mediated by tyrosine phosphatases, the SOCS (suppressor of cytokine signalling) feedback inhibitors and PIAS (protein inhibitor of activated STAT) proteins. Also the cross-talk between the JAK/STAT pathway with other signalling cascades is discussed. [less ▲]

Orientational constraints of the gp130 intracellular juxtamembrane domain for signaling

in Journal of Biological Chemistry (2002), 277(30), 26959-65

The glycoprotein 130 (gp130) is the common signal transducing receptor chain of the interleukin-6 family of cytokines. Here we investigated the requirements for transfer of the information given by ligand ... [more ▼]

The glycoprotein 130 (gp130) is the common signal transducing receptor chain of the interleukin-6 family of cytokines. Here we investigated the requirements for transfer of the information given by ligand binding to the cytoplasmic domain of gp130. It is demonstrated that the box 1/2 region has to be located membrane-proximally in order to bind and activate Janus kinases. To test the possible requirement of an alpha-helical orientation, we inserted 1-4 alanine residues into this juxtamembrane intracellular region. The insertion of one alanine results in a strongly reduced activation of STAT1 and STAT3, whereas insertion of three alanine residues leads to a stronger STAT activation. These results suggest that gp130-mediated activation of STATs is sensitive to rotational changes around the receptor axis perpendicular to the membrane. Surprisingly, insertion of 1, 2, 3, or 4 alanine residues into this juxtamembrane region leads to successive impairment but not abolishment of Janus kinase and receptor phosphorylation, supporting the finding of sensitivity of Janus kinases toward changes in distance of box 1/2 from the plasma membrane. We suggest a new model concerning the gp130 activation mode in which the relative orientation of the cytoplasmic regions seems to be critical for further signal transduction. [less ▲]

Non-redundant signal transduction of interleukin-6-type cytokines. The adapter protein Shc is specifically recruited to rhe oncostatin M receptor

in Journal of Biological Chemistry (2001), 275(52), 40742-8

The common use of the cytokine receptor gp130 has served as an explanation for the extremely redundant biological activities exerted by interleukin (IL)-6-type cytokines. Indeed, hardly any differences in ... [more ▼]

The common use of the cytokine receptor gp130 has served as an explanation for the extremely redundant biological activities exerted by interleukin (IL)-6-type cytokines. Indeed, hardly any differences in signal transduction initiated by these cytokines are known. In the present study, we demonstrate that oncostatin M (OSM), but not IL-6 or leukemia inhibitory factor, induces tyrosine phosphorylation of the Shc isoforms p52 and p66 and their association with Grb2. Concomitantly, OSM turns out to be a stronger activator of ERK1/2 MAPKs. Shc is recruited to the OSM receptor (OSMR), but not to gp130. Binding involves Tyr(861) of the OSMR, located within a consensus binding sequence for the Shc PTB domain. Moreover, Tyr(861) is essential for activation of ERK1/2 and for full activation of the alpha(2)-macroglobulin promoter, but not for an exclusively STAT-responsive promoter. This study therefore provides evidence for qualitative differential signaling mechanisms exerted by IL-6-type cytokines. [less ▲]

Signal transduction of IL-6, leukemia-inhibitory factor, and oncostatin M: structural receptor requirements for signal attenuation

in Journal of Immunology (2000), 165(5), 2535-43

Stimulation of the IL-6R complex leads to Src homology domain containing tyrosine phosphatase 2 (SHP2) recruitment to the receptor subunit gp130 and its subsequent tyrosine phosphorylation. SHP2 is a two ... [more ▼]

Stimulation of the IL-6R complex leads to Src homology domain containing tyrosine phosphatase 2 (SHP2) recruitment to the receptor subunit gp130 and its subsequent tyrosine phosphorylation. SHP2 is a two-SH2 domain-containing protein tyrosine phosphatase that is activated by many cytokines and growth factors. SHP2 counteracts the activation of transcription factors of the STAT family and the induction of IL-6-responsive genes. Tyrosine 759 of gp130, the signal transducing subunit of the IL-6R complex, is essential for the phosphorylation of SHP2. Mutation of tyrosine 759 to phenylalanine leads to an enhanced inducibility of IL-6-dependent genes. Here we demonstrate that no further tyrosines in the cytoplasmic part of gp130 are required for the phosphorylation of SHP2. We also tested whether the tyrosine 759 motifs in both subunits of the gp130 dimer are required for SHP2 association and tyrosine phosphorylation. Interestingly, one SHP2-recruiting phosphotyrosine motif in a single chain of the gp130 dimer is sufficient to mediate SHP2 association to the gp130 receptor subunit and its tyrosine phosphorylation as well as to attenuate IL-6-dependent gene induction. Furthermore, we show that repression of gene induction via Y759 does not require the presence of the SHP2 and STAT recruitment sites within the same receptor subunit, but within the same receptor complex. The Y759 motif in gp130 also attenuates gene induction mediated by the oncostatin M and leukemia inhibitory factor receptor complexes, which both contain gp130 as the shared subunit. [less ▲]

Contributions of leukemia inhibitory factor receptor and oncostatin M receptor to signal transduction in heterodimeric complexes with glycoprotein 130

in Journal of Immunology (2000), 163(12), 6651-8

Leukemia inhibitory factor (LIF), cardiotrophin-1, ciliary neurotrophic factor, and oncostatin M (OSM) lead to heterodimerization of LIF receptor (LIFR) or the OSM-specific receptor (OSMR) with ... [more ▼]

Leukemia inhibitory factor (LIF), cardiotrophin-1, ciliary neurotrophic factor, and oncostatin M (OSM) lead to heterodimerization of LIF receptor (LIFR) or the OSM-specific receptor (OSMR) with glycoprotein (gp) 130, the common receptor subunit for IL-6-type cytokines. Thereby intracellular signaling via Janus kinases (Jaks) and STAT transcription factors is initiated. We investigated the contributions of LIFR and OSMR to signal transduction in the context of heterodimers with gp130. Chimeric receptors based on the extracellular parts of the IL-5R alpha- and beta-chains were generated, allowing the induced heterodimerization of two different cytoplasmic tails. Our studies demonstrate that upon heterodimerization with the gp130 cytoplasmic region, the cytoplasmic parts of both LIFR and OSMR were critical for activation of an acute phase protein promoter in HepG2 hepatoma cells. The membrane-proximal region of LIFR or OSMR was crucial for the ability of such receptor complexes to induce DNA binding of STAT1 and STAT3 in COS-7 cells. Membrane-distal regions of LIFR and OSMR contributed to STAT activation even in the absence of gp130 STAT recruitment sites. We further show that the Janus kinases Jak1 and Jak2 constitutively associated with receptor constructs containing the cytoplasmic part of LIFR, OSMR, or gp130, respectively. Homodimers of the LIFR or OSMR cytoplasmic regions did not elicit responses in COS-7 cells but did in HepG2 cells and in MCF-7 breast carcinoma cells. Thus, in spite of extensive functional similarities, differential signaling abilities of gp130, LIFR, and OSMR may become evident in a cell-type-specific manner. [less ▲]